I awoke in a bed for the first time in days. My joints ached and my eyelids, which had been open for so long, now lay heavy as old hinges above my cheekbones. I wore two pieces of clothing: an assless gown and a plastic bracelet.

I remembered the hallway I had been wheeled down, and the doctor’s office where I told the psychiatrist he was the devil, but not this room. I forced myself up and stumbled, grabbing the chair and the bathroom doorknob for balance. I made it to the toilet, then threw water on my face at the sink, staring into the mirror in the little lavatory. My tousled hair shot out around my puffy face; my head throbbed. I looked hungover.

In those first moments, I remembered the basics about what had landed me in the hospital: Some pseudo-philosophical ranting and flailing brought on by a poorly executed experiment to see how long I could last without sleep.

I was 18, in Italy, on a school-sponsored trip with that pompously misnamed group for American teens who earn As and Bs, the National Honor Society. I stayed up writing all night, and the next morning, on little more than impulse, I decided to go for it.

Why? There are a few layers of “why,” and I will mine them later.

Unlike other basic bodily functions, such as eating and breathing, we still do not fully understand why people need to sleep.

To this day, I am not sure how many consecutive nights I spent awake, but it was at least four. Espresso helped me keep going. So did furiously paced, illogical scribbling in a fat blue pocket notebook. As the sleepless days passed, I experienced the increasingly severe psychological effects common with extended sleep deprivation: I hallucinated, rambled, and lost focus. Toward the end of the ordeal, in New York’s John F. Kennedy Airport, my body was giving out, too. While imposing a monologue on my biology teacher—who, I later learned, thought I was tripping on LSD—I blacked out and slumped mid-sentence. This happened more than once on my final day awake. Sleep specialists call these involuntary collapses “microsleeps.” It’s not hard to see why anybody—a high school chaperone, a parent, a doctor—might view a twitching, crumpling, babbling kid like me as some sort of nutcase. But what happened to me could happen to anyone who stays awake that long, voluntarily or otherwise.

Unlike other basic bodily functions, such as eating and breathing, we still do not fully understand why people need to sleep. There are theories—some think sleep may be the process by which the brain shuts down so it can store the day’s memories. Others, like Dr. Joyce Walseben, a psychiatrist and the former director of Bellevue Hospital’s Sleep Disorders Center, point to sleep’s importance in regulating the body’s hormones. But these theories are not complete.

“It may be the biggest open question in biology,'' Dr. Allan Rechtschaffen, a sleep expert and a professor emeritus at the University of Chicago, told the New York Times in 2003. “While we sleep, we do not procreate, protect or nurture the young, gather food, earn money, write papers, etc.,'' he wrote.

Dr. Steven Feinsilver is a pulmonologist and sleep specialist who said that humans need, on average, seven and one quarter hours of sleep to stay healthy. “Now clearly like all biological things there are probably people who feel great on five hours, and they’re really lucky, and some people who need nine hours, and they’re not so lucky,” Feinsilver said. “Whether you can train that to change, I don’t know.”

Sleep deprivation is nearly as misunderstood as sleep itself, but it can physically and mentally harm people in myriad ways. Losing sleep can cause hallucinations, psychosis, and long-term memory impairment. Some studies have linked sleep deprivation to chronic conditions like hypertension, diabetes, and bipolar disorder. In 2003, neurologists at the University of Pennsylvania found that sleep deprivation over three consecutive nights (in the study, staying awake for 88 hours) as well as chronic sleep loss (in the study, four to six hours of sleep each night for 14 nights) seriously impaired cognitive functions in healthy adults. Also in 2003, Japanese researchers found that total sleep deprivation can cause high blood pressure and has “profound” effects on the immune system.

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In 1989, at the University of Chicago, researchers observed rats which died after being kept awake non-stop for several weeks. (According to a 2009 Slate article, specialists who have looked at the 1989 study dispute which effects of sleep deprivation ultimately killed the rats. It could have been hypothermia brought on by decreased body temperatures, illnesses that arose from damaged immune systems, or severe brain damage.) In July 2012, Chinese soccer fan Jiang Xiaoshan died after staying awake for 11 days to watch all of the European Football Championship. In August, a Bank of America intern died after three days of sleep deprivation.

Feinsilver directs the Center for Sleep Medicine at Mt. Sinai School of Medicine in New York City. He speaks precisely and often adds cheerful “maybes” and “I wonders” into his sentences, taking care to not overstate anything. More than 30 years ago, Feinsilver learned first-hand the toll that sleep deprivation can take. One autumn, when he was an intern in an intensive-care unit, he had to work through every other night for six straight weeks.

“The reason I know it was October was there was a pumpkin at the nursing station, and I hallucinated vividly the pumpkin was talking to me,” he said. “It’s the only time I’ve ever hallucinated in my life.” Ah, he thought for the first time, sleep deprivation resembles psychosis.

According to Walseban, sleep loss can cause psychological damage because sleep regulates the brain’s flow of epinephrine, dopamine, and serotonin, chemicals closely associated with mood and behavior.

“Mood and sleep use the same neurotransmitters,” she said. “It’s very hard to tell if someone has sleep loss or depression.” Walseban added that when these neurotransmitters are disrupted by sleep loss, the chemical changes in the brain can also result in manic feelings and behavior similar to bi-polar disorder: high highs of ecstasy and low lows of depression and anger.

This aligns with my experience; while sleep deprived, I swung from profound bliss and satisfaction, laughing at Renaissance frescos, to deep sadness and rage, grunting like a gorilla one night in a Lucerne hotel room where I chucked empty glass soda bottles at my best friend’s head.

The notion that a person can "catch up" on lost sleep is misconstrued.

When I tried to stay awake for as long as I could, I was an aggrieved, angst-filled teenager. I did it to show that I could, to prove something about myself, and to conquer some adolescent frustrations. I felt that I did not have much time on Earth, and death scared me. I did not really believe in an afterlife, and my fears made me wish I had more hours and years to live. Needing to sleep a third of each day bothered me, and I started staying up late to watch television, read, and write. Eventually I was only sleeping four or five hours each night. One day, I told myself, I would prove how much time sleep stole from us by staying awake for as long as I could and documenting everything I did and accomplished. I imagined that when I could not take it anymore, I would pass out, then sleep long and deep to make up for the extra time awake, and that would be the end of it.

Feinsilver said the notion that a person can “catch up” on lost sleep is misconstrued. “If you’re getting five hours of sleep Monday through Friday, by Friday, you owe yourself like, 10 or 12 hours of sleep,” he said. “It’s not quite that simple. What that means is that, in order for you to catch up on weekends, you’d have to sleep ridiculous hours. And nobody does. You’d have to sleep the seven, plus an extra 12.”

A sleep-deprived person recovers from sleep loss similar to a traveller recovering from a flight; she spends a certain amount of time tiring out her body and can rehabilitate with an equivalent or duplicative amount of recovery time. For each hour spent in a plane, a person needs approximately the same number of days to fully recover from jetlag. In a widely cited paper from 2006, European researchers compared this process to the body’s method of loss and recovery when it chronically loses sleep. The problem, the researchers write, is that many people who chronically lose sleep live in societies where their work and school schedules are not aligned with the body’s circadian rhythms. So they never make up for lost sleep from the nights before, and build up a “sleep debt” that is never repaid. The consequence of chronic sleep debt, they say, is “social jetlag”—a chronic slowing of concentration and hampering of bodily systems. Researchers like Feinsilver and Walseban fear that this affect has been widespread. “We’re a sleep deprived society,” Feinsilver said.

Feinsilver’s memory of the talking pumpkin stayed with him, but he did not decide to pursue sleep research until he won a fellowship to study the ventilatory drive, the mechanism by which the brain sends signals to the lungs and makes a person breathe. At the time, he said, people erroneously thought that sleep apnea was caused by problems with those signals. The research gripped him enough that that he decided to open his own sleep lab. Today, although his focus remains on sleep problems associated with breathing and the lungs, he continues to investigate the other negative effects that sleep deprivation has on the mind and body.

“Definitely, we know that sleep deprivation leads to depression, high blood pressure, weight gain, heart disease, and probably mortality,” he said. People that regularly sleep those seven and a quarter hours have been shown to live longer than those who routinely sleep less or more. He added that lack of sleep disrupts other systems in the body.

Today, I still feel like I have more difficulty concentrating than I did before I stayed awake for several straight days. It might just be my imagination. I will probably never be sure.

“For instance, if you stay up until 3 a.m., you might get very cold,” he said, clarifying that sleep helps to regulate your body temperature. “Your G.I. tract can get messed up. You’re not supposed to eat at three in the morning. It’s a fairly miserable experience.”

Both Feinsilver and Walseben, whose background is in biopsychology, said that these interruptions, as well as the aforementioned neurotransmitter disturbances, can disrupt reaction times and concentration. Walseben noted that certain famous historical accidents—such as the the spill of the Exxon Valdez oil tanker—were caused by sleep deprived workers. More recently, a Metro North train in New York may have derailed when a sleep-deprived engineer nodded off at the helm. Feinsilver said that lack of sleep is also a leading cause of automobile accidents, mainly because when the brain is deprived of sleep, it becomes particularly difficult to perform prolonged, repetitive tasks like driving.

While a person sleeps, her cells undergo a cycle of repair that provides both oxygen and glucose. When a person stays up all night, the brain’s cells are denied the products of this cycle, severely hampering the organs’ reactions to stimuli and instructions. “Every cell in our body needs food and it produces waste, so all those things occur in a regular, regimented way when we’ve slept well. And when we interfere with that, systems go out of sync,” Walseben said.

Feinsilver said that while we sleep, the blood stream is cleared of a substance that researchers call “substance S.” Many believe substance S is adenosine, a byproduct of energy production that cells release into the blood throughout waking hours. He said that without sleep, the blood gets clogged with substance S, slowing a person down from head to toe.

“It looks like there’s a toxic substance building up in you, where the more you’re awake, the more you see this stuff floating around the bloodstream, and the only way to get rid of it is to sleep,” he said.

While I was awake in Europe, my reaction time was horribly off and my ability to concentrate fell apart, and I became increasingly clumsy and weak. Today, I still feel like I have more difficulty concentrating than I did beforehand. It might just be my imagination. I will probably never be sure.

Many sleep researchers study people who have partial sleep deprivation. These subjects have social jetlag; in a typical sleep lab, they might sleep four hours or so every night for one week. But the experts I interviewed said that less is known about total sleep deprivation and its lasting impacts because researchers have moral concerns about forcing people to stay awake.

“Once you are up all night, by mid-afternoon, it becomes unbearable,” Feinsilver said. “You can do it, but it’s really torture.”

“You know what people might be doing that?” he added. “The army.”

Because sleep deprivation leaves no marks and is believed to break a detainee's will, the tactic has been adopted by government and security forces.

A 2007 report on American torture tactics—written by non-governmental organizations Physicians for Human Rights and Human Rights First—has a section on sleep deprivation that begins with descriptions of a Soviet gulag. In The Gulag Archipelago, Alexandr Solzhenitsyn lists sleeplessness as one of 31 methods that his captors used to break a prisoner’s will. “Sleeplessness befogs the reason, undermines the will, and the human being ceases to be himself, to be his own ‘I,’” Solzhenitsyn writes. He says that guards in the gulag kept prisoners awake for up to five days by perpetually standing them up or by kicking them when their eyes drooped. The author quotes an inmate who endured this, listing his many symptoms, including chills, eyes “dried out as if someone were holding a red-hot iron in front of them,” a swollen and prickling tongue and a throat racked with spasms. “Sleeplessness was a great form of torture: it left no visible marks and could not provide grounds for complaint even if an inspection—something unheard of anyway—were to strike on the morrow,” Solzhenitsyn writes.

Because sleep deprivation “leaves no marks” and is believed to break a detainee’s will, across the world, the tactic has been adopted by government and security forces, notably by Chilean dictatorAugusto Pinochet in the 1970s. Most notoriously, sleep deprivation has been used on several prisoners at the United States’ Guantánamo Bay prison camp in Cuba.

In the middle of the night, on May 7, 2004, American officers unshackled Afghan Guantánamo detainee Mohammed Jawad; they moved him to another cell, and re-shackled him. Three hours later, Jawad was unshackled, moved, and re-shackled again. Over 14 days, Jawad was moved from cell to cell 112 times. In response to motions filed by Jawad and the ACLU, the military claimed in court that, as a result of the tactic, Jawad had not suffered permanent physical harm, and that the long-term psychological damage to Jawad had been “unclear.” But some specific effects that this program had on Jawad are known. According to reports by the Associated Press and Jawad’s lawyers, he lost 10 percent of his body weight while sleep deprived. In a legal claim against the government arguing that Jawad’s imprisonment was illegal under habeus corpus, ACLU lawyers also wrote that while kept awake, Jawad had blood in his urine. “The torture, cruelty, and harsh treatment to which Mohammed has been subjected throughout his six years in U.S. custody have resulted in severe and ongoing psychological harm,” they concluded.

Rather than kicking prisoners, as the Soviets did, Guantánamo guards kept prisoners awake by chaining their feet and wrists to the floor of their cell, so they could not fall over without being caught by the chains, and moving prisoners between cells every two or three hours. This sleep deprivation program was referred to as the “frequent-flyer” program, or “Operation Sandman,” and was used against at least17 GITMO detainees, according to the military’s ownlogs kept at the prison in 2003 and 2004. In memos authorizing the program that were de-classified in 2009, Justice Department lawyers asserted that sleep deprivation works well as an interrogation technique, because it breaks down detainees’ ability to resist coercion, and because it decreases prisoners’ tolerance for physical pain. In 2012, a letter from British detainee Shaker Aamer asserted that despite being formally banned in 2009, the frequent flyer program was still in use at the prison.

As for Jawad, he was originally taken to Guantánamo for allegedly throwing a grenade into a jeep in Kabul, in December 2002, severely wounding two American Special Forces soldiers and their translator. On Christmas Day that year, he tried to commit suicide by repeatedly banging his head against one of his cell walls. His sleep deprivation program began four and a half months later.

In hindsight, I conducted my experiment inelegantly, under terrible conditions. In the first days of the trip, I was already only sleeping about four or five hours each night, so I began prematurely fatigued. A better scientist might have begun on full rest.

By the third day, I had two theories about the origin of the universe that I was certain were true and would change the world. The days all blend together now, but at some point I tried to speak exclusively in rhyme. On another day, I renounced speech altogether. I remember telling people that circles were divine and instituting a policy of smacking my head when I made mistakes, finally breaking my own glasses with one blow. At a stop in Austria, I stole a kaleidoscope from a mountainside gift shop, and at a cultural night in Switzerland, I volunteered to yodel for the crowd, all too confidently. I bought and wore a headband I refused to remove.

I remember realizing the obvious while waiting for our flight home: that this whole not-sleeping thing was actually inefficient, because I could accomplish more in fewer hours on full rest. I resolved to sleep on the plane home, but when I closed my eyes, my head spun, and I heard a woman’s soothing baritone voice. On the bus ride home from JFK airport, I thought that if I concentrated hard enough, I could jump out of our bus onto the highway, land at a run, and sprint on—to where? I have no idea. Luckily for me, our driver refused to open the bus’s door. I remember thinking I was dead, and that I had landed in a very Earthlike eternity.

We arrived at the high school, and my chaperones had me stay on the bus. They went outside and spoke to my parents. When I sat in the car, my mother asked me through tears about my trip while my father drove in silence. Within minutes we were at the hospital, where I was placed in a wheelchair, asked if I had smoked crack or taken LSD, and peed in a cup. I demanded that my brother drive to the hospital from his home, three hours away in Philadelphia, so I could ask him about astrophysics. He came. I bestowed the headband I had been wearing on my father. He put it on. Eventually I agreed to take the medication they handed me. I do not remember what happened next.

Later that first morning in the hospital, I sat at a table with a nurse in a bright, fluorescent room—all yellow light and white Formica—where several other pairs of people conversed. My legs and elbows shook. A nurse told me that I had been asleep for two days. She asked me if I remembered what had happened. When I answered, stringing the events together became more troublesome than I anticipated. I felt myself sway and I heard my words jumble. It was frustrating. I chuckled between sentences and glanced around the room.

There were holes in my memory and in my logic. It all had something to do with existence, productivity, efficiency. My grand theories had made sense in my head while sleep deprived, but now, for some reason they no longer did. The nurses and doctors responded by prescribing me anti-psychotic medication. This was 2004, and I was 18. It was a common age to be diagnosed with a mental disorder.

I believed that in staying awake for consecutive nights, the effects on my mind and body would differ from the one sleepless night only in degree. Obviously, I was wrong.

Throughout the next week in the hospital, I spoke every day with the first nurse and the head psychiatrist. My main goal was to convince them I was fine, so I could get the hell out of there. I was assigned to art therapy, where I tried to draw images that evoked solemnity and composure—it was all about showing I was fine, not feeling fine—including the most maudlin and transparent of these, a blue and green earth with stars and the word “Peace” floating above it. This had all been a misunderstanding.

When I finally went home, a week after entering the hospital, I had prescriptions and appointments with a psychologist and a psychiatrist. The psychologist believed I was not crazy. She and my parents argued with the psychiatrist about the medication, who eventually agreed to first wean me off an anti-psychotic by transitioning me to an anti-depressant, and then to wean me off of the anti-depressant entirely. This process lasted four months. Before the sleepless nights, I had been a strong test taker, and I never felt nervous while writing. On the contrary, writing had been one of the few tasks that gave me confidence, even calm. But in the middle of a standardized test in May, I shook with anxiety and asked to leave the room. (I later finished the test by myself under the supervision of a guidance counselor.) In June, night after night, I sat down a write a research paper, and my head pounded and swirled.

No doctors or psychiatrists suggested that this had all happened because of sleep deprivation. They were sure it was something endemic that had caused the hallucinations and the existential rambling. I spent much of that summer alone, learning to trust my mind again by reading and writing and speaking with my family. I left for college in the fall, off medication, unsure of how my foray into sleep deprivation and its ensuing madness would affect me, and I worried it would creep up on me again. In the nine years since then it has not. I feel like I might have more trouble concentrating, but it’s unclear whether this trouble stems from sleep deprivation, or from that vortex of distraction, the Internet.

Sleep remains mysterious to researchers like Walseben and Feinsilver. Despite the negative effects they have observed and others have researched, the definitive reasons why people need to sleep remain unknown. We only know some of the negative effects that occur over time, and that we require sleep to survive.

“Clearly, even though we cannot tell you why you need to sleep, you must sleep,” Walseben said. “It’s a basic physiological function that none of us have been able to get away without. Even though you may think you can, bad things tend to happen.”

Anyone who has endured one night without sleep knows that functioning through the next day can be uncomfortable and frustrating. It is fair to call a sleepless night a common experience. But I believed that in staying awake for consecutive nights, the effects on my mind and body would differ from the one sleepless night only in degree. Obviously, I was wrong. It seems to me that this common experience and misunderstanding — and the things that researchers still do not understand about sleep — has created a public that all too readily sleep deprives itself and cavalierly imposes sleep deprivation on others. In keeping ourselves and our prisoners awake, we do not really know what we are doing. We are fumbling in the dark.